JP2012149613A - Variable displacement turbocharger, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable displacement turbocharger that prevents abnormal wear of a sliding part, and a method of manufacturing the same.SOLUTION: The variable displacement turbocharger includes a crankshaft 24C for adjusting a blade angle of a nozzle vane 30 of a turbine 21, and a bush for supporting the crankshaft 24C outside a turbine housing 26. A coating 10 with molybdenum disulfide particles and graphite dispersed in polyamide imide resin is formed at a support portion supported by the crankshaft 24C.

Description

  The present invention relates to a variable displacement turbocharger having a nozzle vane with variable blade angle in a turbine, and more particularly, a variable displacement turbocharger with improved wear resistance of a crankshaft of a nozzle blade angle adjusting mechanism for adjusting the blade angle of the nozzle vane. And a manufacturing method thereof.

  A turbocharger is installed in a diesel engine for a vehicle. Generally, a fixed capacity (conventional) turbocharger is used. However, since 2011, regulations will be strengthened in North America and Europe. In order to apply, it has been decided to adopt a variable capacity turbocharger (referred to as VNT or VGT) instead of a fixed capacity.

  The conventional variable capacity turbocharger mounted on the vehicle diesel engine is one in which nozzle vanes are provided on the turbine side to control the exhaust gas flow rate as shown in Patent Documents 1 and 2, which are shown in FIGS. explain.

  As shown in FIG. 9, the variable capacity turbocharger 20 is configured by connecting a turbine 21 and a compressor 22 by a bearing housing 29, and the turbine 21 is provided with a turbine capacity variable mechanism 24.

  The turbine 21 includes a turbine impeller 25 and a turbine housing 26 that surrounds the turbine impeller 25 and into which exhaust gas is introduced. The compressor 22 surrounds the compressor impeller 27 and the compressor impeller 27, and a compressor housing 28 that introduces intake air. It consists of. The turbine impeller 25 and the compressor impeller 27 are connected by a turbo shaft 23, and the turbo shaft 23 is accommodated in a bearing housing 29 and supported by a bearing portion (not shown) provided in the bearing housing 29.

  As shown in FIGS. 7 to 9, the turbine capacity varying mechanism 24 includes a large number of nozzle vanes 30 provided at variable intervals along the circumferential direction of the nozzle throat portion 26 a of the turbine housing 26, and these nozzle vanes. Nozzle blade angle adjustment ring 32 connected 30 through a link plate 31, and a crank lever 33 for engaging the groove 32 a of the nozzle blade angle adjustment ring 32 and rotating the nozzle blade angle adjustment ring 32, The crankshaft 34C is connected to the crank lever 33 and extends out of the turbine housing 26, the bush 34B is provided in the bearing housing 29 and rotatably supports the crankshaft 34C, and is connected to the extended crankshaft 34C. A control link 35 for rotating the crankshaft 34C, and its control A driving device 36. which a motor for driving the link 35.

  As shown in FIG. 8, the control link 35 includes a first drive lever 37 connected to the drive device 36, a second drive lever 38 connected to the crankshaft 34C, and the first and second drive levers 37, 38. The control rod 40 includes link pins 39a and 39b to be connected.

  As shown in FIG. 9, the blade capacity of the nozzle vane 30 is adjusted by the turbine capacity varying mechanism 24. As a result, the control rod 40 reciprocates when the drive device 36 rotates by a predetermined angle, whereby the crankshaft 34 rotates by a predetermined angle. At the same time, the crank lever 33 rotates and the nozzle blade angle adjustment ring 32 rotates by a predetermined angle, whereby the blade angle of the nozzle vane 30 is adjusted via the link plate 31, and the nozzle throat portion 26a is moved from the turbine housing 26. The rotational speed of the turbine impeller 25 can be varied by adjusting the inflow angle and the capacity of the exhaust gas flowing into the turbine impeller 25 through the turbine impeller 25.

Japanese Patent Laid-Open No. 05-296053 JP 2004-270472 A

  By the way, although the crankshaft 34C and the bush 34B are provided outside the turbine housing 26, the crankshaft 34C and the bush 34B are exposed to a high temperature of 300 ° C. or higher even in the atmosphere outside the turbine housing 26. As the crankshaft 34C rotates, the rotational sliding surface has a problem that the frictional resistance increases due to the tilting of the crankshaft 34C.

  Conventionally, the bush 34B and the crankshaft 34C are formed of SUS, and the sliding surface is chromized (surface hardening treatment with chromium element) or hardening treatment, nitriding, carburizing, DLC coating (diamond-like coating) It has been proposed to use Trivalloy T400 alloy (registered trademark), Hastelloy (registered trademark), and the like.

  However, there is a problem that even if the material strength is enhanced, mechanical friction is inevitable because it is used in a high temperature environment, and abnormal wear cannot be prevented.

  Accordingly, an object of the present invention is to provide a variable capacity turbocharger that can solve the above-described problems and can prevent abnormal wear even if sliding portion wears, and a method of manufacturing the same.

  In order to achieve the above object, a first aspect of the present invention provides a variable capacity turbocharger having a crankshaft for adjusting a blade angle of a nozzle vane of a turbine and a bush supporting the crankshaft outside the turbine housing. The variable capacity turbocharger is characterized in that a film in which molybdenum disulfide particles and graphite are dispersed in a polyamide-imide resin is formed on a support portion supported by the structure.

  According to a second aspect of the present invention, there is provided a variable capacity turbocharger manufacturing method comprising a crankshaft for adjusting a blade angle of a nozzle vane of a turbine and a bush supporting the crankshaft outside the turbine housing. 20 to 30 parts by mass of molybdenum disulfide particles and 1 to 10 parts by mass of graphite, a binder is added thereto, this is applied to the outer peripheral surface of the crankshaft and dried, and this is repeated several times. This is a method for manufacturing a variable capacity turbocharger, characterized in that after forming the thickness to 30 ± 10 μm, this is fired to form a film.

  The invention according to claim 3 is the method of manufacturing a variable capacity turbocharger according to claim 3, wherein the coating is formed after the outer peripheral surface of the crankshaft is subjected to chromization or nitriding.

  The present invention provides a crankshaft having high slidability and excellent wear resistance even in a high temperature environment by forming a film in which molybdenum disulfide and graphite are dispersed in polyamide-imide resin on a sliding surface. It has an excellent effect of being able to be a bush.

It is a figure which shows one Embodiment of the crankshaft and bush in the turbine capacity | capacitance variable mechanism of the variable capacity | capacitance turbocharger of this invention. It is a figure explaining the abrasion resistance and sliding property of the film | membrane formed in the sliding surface of the crankshaft and bush which comprise the turbine capacity | capacitance variable mechanism of the variable capacity | capacitance turbocharger of this invention. It is a figure which shows the abrasion resistance test result in this invention and a prior art example. It is a figure explaining abrasion of the sliding surface in the past. It is a perspective view explaining the force which acts on the crankshaft and bush in a turbine capacity variable mechanism. It is a figure explaining the state which a crankshaft tilts with the force which acts on a crankshaft and a bush in FIG. It is a perspective view which shows the detail of the nozzle vane and blade angle adjustment ring structure of a variable capacity | capacitance turbocharger. It is a perspective view which shows the detail of the control link of a variable capacity | capacitance turbocharger. It is a whole sectional view of a variable capacity turbocharger.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  First, the basic configuration of the variable capacity turbocharger is as described with reference to FIGS. 7 to 9, and the detailed description thereof is omitted.

  FIG. 1 shows a nozzle blade angle adjusting ring, a crankshaft, a bush and a control link in the turbine capacity varying mechanism of the present invention. FIG. 1 (a) is an overall view thereof, and FIG. The principal part assembly perspective view of the nozzle blade angle adjustment ring 32, the crank lever 33, the crankshaft 34C, the bush 34B, and the control roll link 35 is shown.

  As shown in FIG. 1A, the nozzle blade angle adjustment ring 32 is formed with a groove 32 a that engages with the crank lever 33. As shown in FIG. 1B, the crank lever 33 has an engagement pin 33a that engages with the groove 32a of the nozzle blade angle adjustment ring 32, and a boss portion 33b that connects the lower end of the crankshaft 34C. The crankshaft 34C is rotatably supported by a bush 34B, and the bush 34B is supported by the bearing housing 29 described with reference to FIG.

  The crankshaft 34C is connected to the second drive lever 38 of the control link 35, and the pin 39b of the control rod 40 is provided on the second drive lever 38. In this example, the pin 29b is fixed to the second drive lever 38. However, as shown in FIG. 8, the pin 29b is rotatably fitted to the second drive lever 38 and fixed to the control rod 40. Either may be provided.

  In the present invention, the coating 10 having wear resistance and self-lubricating property is formed on the sliding surface of the outer peripheral surface of the crankshaft 34C and the inner peripheral surface of the bush 34B, particularly on the inner peripheral surface of the bush 34B.

  Further, these sliding surfaces are subjected to chromization treatment and nitriding treatment before the film formation, and the film 10 is formed on the outer peripheral surface of the hardened layer.

The component of this film 10 is
(A) Polyamideimide resin 55-65 parts by mass (B) Molybdenum disulfide particles 20-30 parts by mass (C) Graphite 1-10 parts by mass (D) Pigment (inorganic powder) 5-15 parts by mass.

  (A) As the polyamideimide resin, one having heat resistance of 260 ° C. or higher and having a number average molecular weight of 2000 to 8000 before drying or baking is used.

  (B) Molybdenum disulfide particles are particles excellent in self-lubricity, and those having an average particle diameter of 1 to 2 μm are used.

  (C) As graphite, it is preferable because it has excellent self-lubricating property and has lubricity even if it is worn away and peeled off from the film, and has an average particle diameter of 1 to 2 μm.

  (D) The pigment is a powder whose surface is gray, and white inorganic powder such as calcium carbonate is used. This inorganic powder is used to fix (B) molybdenum disulfide and (C) graphite particles in the resin so that they are not easily separated from the polyamide-imide resin.

  A solvent (N-methyl-2-pyrrolidone (NMP)) is added to the components (A) to (D) to form a film-forming resin precursor.

  After forming a coating film on the inner peripheral surface of the bush 34B (or the outer peripheral surface of the crankshaft 34C) by spray coating or the like, the film-forming resin precursor is heated and dried at 70 to 90 ° C. for 20 minutes or more. This spray coating and drying are repeated 3 to 5 times, and finally a coating film having a thickness of 30 ± 10 μm, preferably 30 μm is formed, and then the coating film is baked by baking at 230 ° C. ± 10 ° C. for 45 ± 5 minutes. The film 10 is formed by

The characteristics of this film 10 are
Friction coefficient 0.06 (typical value)
Cross-cut test 100/100 (JIS K 5400)
Pencil hardness 5H
Heat resistance No change after heating at about 600 ° C. for 30 minutes.

  In addition, the abrasion resistance test was a test piece that was subjected to a test after being heated to 360 ° C. × 20 hours and then exposed to a humid environment at 60 ° C. × 90% × 100 hours. It was confirmed to withstand sliding friction.

  In this wear test, a SUS440C ball was applied to the test piece, a load of 1 kgf was applied, the sliding speed was 1.5 m / sec, the friction radius was 16.5, the rotation speed was 870 rpm, and the friction coefficient of the link pin was 0.3. In addition, the number of times to rise was measured.

  The bush 34B (or the crankshaft 34C) is chromized and then painted, but may be sandblasted to roughen the surface.

  Next, the operation of the film 10 will be described.

  FIG. 5 is a perspective view for explaining the force acting on the crankshaft and the bush in the turbine capacity varying mechanism.

  During the drive link for adjusting the blade angle of the variable capacity turbocharger, the second drive lever 38 side on the control link 35 side and the crank lever 33 of the nozzle blade angle adjusting ring 32 are almost as shown by the arrows in the figure. A force in the opposite direction acts. For this reason, a moment load acts on the crankshaft 34C as shown in FIG. 6A, and the crankshaft 34C tilts as shown in FIG. 6B, and the surface pressure at both end portions becomes extremely high. For this reason, along with the rotation and swing, a strong edge contact occurs, and the wear easily proceeds rapidly.

  FIG. 4 shows the state of the inner peripheral surface of a conventional bush 34B and the outer peripheral surface of the crankshaft 34C that are not formed with a film.

  In this conventional example, as shown in FIG. 4A, even if the surface of the crankshaft 34C is subjected to nitriding treatment, micron-order machining roughness remains, and the edge load is further increased by the tilting of the crankshaft 34C. As a result, the contact stress becomes extremely high, micro-breakage of the contact portion occurs, and as shown in FIG. 4B, the hardened layer of the contact portion is chipped off to be broken pieces 34P and disappear from the sliding surface. . The crankshaft 34C and the bush 34B are in an environment in which both ends are semi-closed with a plate or the like, and a hard broken piece 34P may stay for a long time, causing further wear.

  On the other hand, in the present invention, the above-described abnormal wear can be prevented by forming the film 10.

  This will be described with reference to FIG.

  FIG. 2 shows an enlarged schematic view of the cross section of the coating 10 formed on the crankshaft 34C (or bush 34B).

  First, as shown in FIG. 2A, immediately after the formation of the coating 10, the crankshaft 34C (or the bush 34B) in which the coating 10 in which the molybdenum disulfide particles 11B and the graphite 11C are dispersed is formed in the polyamideimide resin 11A. In this state, the bush 34B (or the crankshaft 34C) is in contact.

  Thus, by including the molybdenum disulfide particles 11B and the graphite 11C in the film 10, the sliding performance of the sliding surface becomes good even at high temperatures.

  Here, when the crankshaft 34C is inclined, the contact stress at the edge portion 34E increases, and as shown in FIG. 2B, the edge portion bites into the coating 10, and the coating 10 or the molybdenum disulfide particles 11B Graphite 11C is released, and the edge portion 34E comes into contact with the hardened layer of the crankshaft 34B as shown in FIG. 2 (c). By suppressing the abrasion that causes peeling (mirror-like wear), the wear resistance performance of the hardened layer and the base material can be maximized.

  As described above, the present invention forms the coating 10 made of polyamideimide resin on the sliding surfaces of the crankshaft 34C and the bush 34B, and even if the coating 10 is worn, molybdenum disulfide dispersed in the polyamideimide resin Graphite becomes a solid lubricant, which eliminates the problem of surface roughness and finally allows the sliding surface to be in a mirror-finished state.

  Next, the results of a wear test using the crankshaft 34C and the bush 34B of the present invention and conventional examples 1 and 2 will be described with reference to FIG.

  In FIG. 3, in the present invention and the conventional examples 1 and 2, the crankshaft 34C and the bush 34B are both SUS, and in the conventional examples 1 and 2, both nitride layers are 50 μm. In the present invention, the nitride layer is 50 μm and the film is 30 μm. Is given.

  As test conditions, vibration acceleration for acceleration was applied at 30 G. This wear rate is about three times the actual vibration.

  As a result, in the conventional examples 1 and 2, the hardened layer (50 μm) is worn in 130 hours, whereas in the present invention, the wear is very slow, and only about 1/2 of the film is generated even in the three times the test time. The expected life time was 1142 (hr) or more, and it was confirmed that the life extension effect can be prolonged by 8.794 times or more than the conventional one.

10 Coating 24 Turbine capacity variable mechanism 30 Nozzle vane 34C Crankshaft 34B Bush

Claims (3)

  In a variable capacity turbocharger having a crankshaft for adjusting the blade angle of a turbine nozzle vane and a bush for supporting the crankshaft outside the turbine housing, a support portion for supporting the crankshaft by the bush is installed in a polyamideimide resin. A variable capacity turbocharger in which a film in which molybdenum sulfide particles and graphite are dispersed is formed.   In a manufacturing method of a variable capacity turbocharger having a crankshaft for adjusting a blade angle of a turbine nozzle vane and a bush supporting the crankshaft outside the turbine housing, 55 to 65 parts by mass of polyamideimide resin, molybdenum disulfide particles 20 to 30 parts by mass, graphite to 1 to 10 parts by mass, a binder is added thereto, this is applied to the outer peripheral surface of the crankshaft and then dried, and this is repeated several times to obtain a film thickness of 30 ± 10 μm. Then, this is baked to form a film, and a method for manufacturing a variable capacity turbocharger.   The manufacturing method of the variable capacity | capacitance turbocharger of Claim 2 which formed the said film | membrane after performing the chromization process or the nitriding process on the outer peripheral surface of the said crankshaft.